In the arrangement shown in the figure all surfaces are frictionless, the masses of the block are m₁ = 20kg and m₂ = 30kg. The accelerations of masses m₁ and m₂ will be if F = 180N.

The only horizontal force acting on m1 is the tension in the string.

As the string is mass less, the tension in the string is the force applied at the free end of the string.

For m₁ block 180 = m₁ a₁
${\text{a}}_{\text{1}}\text{=}\frac{\text{180}}{\text{20}}{\text{=\hspace{0.17em}9m/s}}^{\text{2}}{\text{;\hspace{0.17em}a}}_{\text{2}}\text{=\hspace{0.17em}0}$

since the net horizontal force on the block is zero